Pressurized solution feed system for pH control

ABSTRACT

A method and appartus for controlling the pH of a water stream using carbon dioxide in which carbon dioxide at a selected pressing and flow rate is mixed with a carrier water, also at a selected pressure and flow rate, and the carbon dioxide-carrier water mixture is injected into the water steam, which is at a lower pressure, thus allowing the carbon dioxide to come out of the solution, contact the water stream and correspondingly adjust the pH of the water stream.

This is a continuation of copending application(s) Ser. No. 08,182,766filed on Jan. 14, 1994.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to the field of treat potable or wastewater so as to reduce the pH of the water, and relates more specificallyto a method and apparatus for injecting carbon dioxide into potable orwaste water having a high pH level so as to reduce the pH of the water.

2. Prior Art

During its treatment phase, potable or waste water may have a high pHlevel, high being any pH over a pH of 9. Such a pH is unacceptable for afinal, treated water product and this pH must be reduced prior toallowing the treated water into general use. For example, most watertreatment plants are required to maintain an effluent pH of between 6and 9. Therefore, any water being treated having a pH of higher thanabout 9 should have its pH lowered before leaving the plant.

One method for treating water so as to lower its pH is to inject carbondioxide gas into the water. Several methods currently are used to injectthe carbon dioxide into the water. The most accepted method is to injectthe carbon dioxide into the water by a direct gas feed through some theof diffusion system in a recarbonation basin; in effect, a bubbler. Amechanical mixing means can be used in combination with this method forbetter efficiency. Another method for injecting carbon dioxide intowater is to aspirate the carbon dioxide into a stream of water using aventuri the eductor. In this method, the carbon dioxide is injected intothe stream of water and carried along with the stream of water to a gridsystem located in a basin or a pipeline.

Both the direct gas feed method and the venturi method of injectingcarbon dioxide gas into water allow for the control of the pH and thestabilization of the treated water. However, it is difficult to controlthe efficiency of the carbon dioxide gas usage. Both of these processesrequire the use of a relatively large contact basin, a relatively longcontact time or large amount of carrier water, all of which inherentlyare inefficient. Therefore, the need exists for a system for injectingcarbon dioxide into water to control the pH of the water which has agreater efficiency per unit of carbon dioxide used using either lesscarbon dioxide or less components. A direct carbon dioxide injectionmethod and apparatus in which the amount of carbon dioxide injected intothe water stream is controlled, and the elimination of the recarbonationbasin would satisfy this need, and result in increased efficiency andlower cost. It is to this need that the present invention is directed.

BRIEF SUMMARY OF THE INVENTION

The present invention takes carbon dioxide gas at an elevated pressureand injects this gas into carrier water, also at an elevated pressure.The carrier water-carbon dioxide solution, still at an elevatedpressure, then is injected into the water to be treated, which typicallyis at atmospheric pressure, through a unique diffuser system. As thepressurized carrier water-carbon dioxide solution is injected into thewater to be treated, the carbon dioxide expands due to the lowerpressure of the water to be treated and the excess carbon dioxide burstsforth out of solution as minute bubbles released into the main stream ofwater. The carbon dioxide bubbles mix rapidly with the main stream ofwater, thus reducing the pH of the main stream of water. In most cases,95% of the chemical reaction between the main stream of water and thecarbon dioxide gas is immediate, thus eliminating the need for arecarbonation basin or an extended contact area or contact time.

The apparatus comprises means for injecting the elevated pressure carbondioxide gas into the elevated pressure carrier water. The carrierwater-carbon dioxide solution then passes through in-line static mixingmeans for further mixing. After the static mixing means, a serpentinepipe system means is provided, allowing additional contact time betweenthe injected carbon dioxide and the carrier water stream. The carrierwater-carbon dioxide solution then is injected into the main waterstream through a diffuser. This diffuser is designed to maintain systempressure, thus forcing the CO₂ gas to remain in the carrier watersolution. The super saturated water-CO₂ solution mixture then passesthrough the diffuser into the main stream of water. At this moment,excess CO₂ gas is released as an effervescence, immediately beingabsorbed in the main stream water. The diffuser is also designed toenhance mixing of the two solutions.

The preferred solution injector is triangular, prismatic, andpreferrably somewhat concave on two sides, and is inserted normal to thedirection of flow of the water stream. One triangular end of thediffuser connects to an inlet feed-line for the saturated solution,while the second triangular end is solid. Two of the rectangular sidesof the diffuser have a plurality of small holes therethrough allowingcommunication between the interior of the diffuser and the water stream.The vertex of two sides faces upstream and the third side facesdownstream relative to the direction of flow of the water.

The saturated solution of elevated pressure is fed to the diffuserthrough a feed-line. The pressurized solution, upon encountering thelower pressure water stream, equilibrates. At this precise moment, theexcess CO₂ gas in the carrier water bursts forth in the form of minuteCO₂ gas bubbles.

As the vertex of the two sides of the diffuser faces upstream, two sidesof the diffuser effectively are in the flow path of the water stream.This, along with the velocity at which the saturated carrier watersolution exits the diffuser assembly, allows for effective mixing andgreater contact time between the lower pH carrier water, expanded CO₂gas and the main water stream. The positioning of the third side of thediffuser, facing downstream, creates a vortex in the main water streamflow, thus allowing additional mixing.

Accordingly, it is an object of the present invention to provide asolution feed system for injecting carbon dioxide into a water streamfor controlling the pH of the water stream.

It is another object of the present invention to provide a solution feedsystem in which recarbonation basins and/or extended contact areas ortimes are unnecessary.

Another object of the present invention is to provide a solution feedsystem in which elevated pressure carbon dioxide first is mixed withelevated pressure carrier water, and the elevated pressure carrierwater-carbon dioxide solution then is injected into the water to betreated.

Still another object of the present invention is to provide a solutionfeed system in which carbon dioxide mixes almost immediately with thewater to be treated, thus reducing the overall contact time neededbetween the carbon dioxide and the water to be treated.

It is yet a further object of the present invention to provide asolution feed system which can be operated continuously and eliminatesthe need for a batch treatment apparatus.

Another object of the present invention is to provide a solution feedsystem for controlling the pH of a water stream which is efficient inoperation, simple in construction and manufacture, and easy to operate.

These objects, and other objects, features and advantages of the presentinvention, are described in the following Detailed Description of aPreferred Embodiment and the appended figures, in which like referencecharacters represent like parts throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the entire solution feed system of the presentinvention;

FIG. 2 is a side view of the injection apparatus of the presentinvention;

FIG. 3 is a side view of the preferred injector used in the presentinvention; and

FIG. 4 is a cross-section of the preferred injector shown in FIG. 3,taken along 4'--4'.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to FIG. 1, a general schematic of the entire solution feedsystem is shown. In general, the solution feed system comprises acarrier water-carbon dioxide solution creation means 50, also called thecontrol panel and shown in greater detail in FIG. 2, a carbon dioxidesupply means 60, and an injector means 70. The various components 50,60, 70 are connected using standard piping 35.

The carbon dioxide supply means 60 comprises a liquid carbon dioxidestorage tank 1 in which liquid carbon dioxide is stored until needed.The liquid carbon dioxide is kept at a temperature cool enough to remainliquid by refrigeration unit 2. Vaporizer liquid isolation valve 4allows liquid carbon dioxide to be admitted to a carbon dioxidevaporizer 3 to vaporize the carbon dioxide. Vaporizer vapor isolationvalve 5 allows the vaporized carbon dioxide to be admitted to the top ofthe liquid carbon dioxide storage tank 1.

when running the solution feed system of the present invention,vaporized carbon dioxide from liquid carbon dioxide storage tank 1 isadmitted to a carbon dioxide vapor heater 8 through vapor processisolation valve 7. Within the carbon dioxide vapor heater 8, thevaporized carbon dioxide is heated to an appropriate temperature. Aprimary pressure regulator 10 maintains the carbon dioxide at thedesired pressure before the carbon dioxide is admitted to the carrierwater-carbon dioxide solution creation means or control panel 50. A linepressure relief valve 9 is included in the pressure regulator line forsafety purposes. A pressure gauge 12, separated from the pressureregulator line by gauge isolation valve 11, allows visual checking ofthe pressure of the carbon dioxide vapor. The carbon dioxide thentravels through piping 35 to carrier water-carbon dioxide solutioncreation means or control panel 50.

The carrier water-carbon dioxide creation means or control panel 50comprises the components for creating the desired solution of carbondioxide gas in carrier water. The carbon dioxide is admitted to thecontrol panel 50 through control panel isolation valve 13. The carbondioxide then is strained in carbon dioxide strainer 14 to remove anydebris, and is maintained or brought to the proper desired pressureusing secondary pressure regulator 15. A pressure gauge 17, separatedfrom the carbon dioxide feed line by gauge isolation valve 16, allowsvisual checking of the pressure of the carbon dioxide. A line safetyrelease valve 18 is placed on the feed line for safety purposes. At thispoint, the feed of the carbon dioxide is diverted to one of two lines:either the automatic flow control line comprising automatic controlvalve 21, or the manual flow control line, comprising manual VAREA-meter22.

The preferred path is the automatic flow control line which allowsautomatic flow control of the carbon dioxide feed. The carbon dioxide isadmitted to the automatic flow control line via an isolation valve 20.The flow is regulated using an automatic flow control valve 21, whichpreviously has been set at the desired flow rate, and/or which can beadjusted continuously based on the pH of the treated water, as discussedin more detail below. Any typical automatic flow control valve can beused and in the present example, a Badger Controls one-half inch 807 S.S. valve with "E" trim connected with an EVA-1 actuator is used. Thecarbon dioxide flow is measured by a flow indicator/transmitter 19. Anysuitable flow indicator/transmitter can be used, and in this example, aFoxboro 823DP flow indicator/transmitter is used. The carbon dioxideflow then continues through a second isolation valve 20.

Alternatively, the carbon dioxide flow can be manually maintained. Theautomatic flow control line is closed off using an isolation valve 20while a second isolation valve 20 allows the carbon dioxide feed toenter the manual flow control feed line. The carbon 0 dioxide passesthrough a VAREA-meter 22 to measure its flow rate. Although anyVAREA-meter or other gas flow measurement meter can be used, a Wallace &Tiernan 5210B12208BB406SX VAREA-meter is used in this example. The flowthrough the manual flow control line is regulated using a manual flowcontrol valve 24. Typically, a one-half inch needle valve is employed.Prior to encountering the manual flow control valve 24, the carbondioxide is sent through a one-half inch orifice union. The carbondioxide then continues along the feed path.

After exiting either the automatic flow control line or the manual flowcontrol line, the carbon dioxide is mixed with carrier water C to obtaina carrier water feed solution or mixture having an excess of carbondioxide gas. The carrier water C is supplied to the control panel 50under pressure through a water pressure/flow regulator 27. Thepressurized carrier water C is prevented from back flowing into thecarrier water C feed line by a water back flow preventor 28. The carbondioxide feed, also under pressure, is injected into the pressurizedcarrier water C through an injector 80.

Typically, a ratio of approximately 60 gallons of carrier water C perpound of carbon dioxide gas is used and preferred. The carrier water Cis pressurized to a minimum of 50 psig. The carbon dioxide typically issupplied to the carrier water C at between 60 and 75 psig. In general,the present invention is designed to allow flow rates of carbon dioxideof from about 5 to 2000 pounds per hour. However, carbon dioxide can besupplied to the carrier water C at a pressure of anywhere between about30 and 300 psig, and a flow rate of anywhere between about 5 and 5000pounds per hour. The system is designed to handle flow rates of carrierwater C of approximately 100 gallons per minute at 50 psig, but can bealtered to handle flow rates of carrier water C of anywhere betweenabout 25 and 2000 gallons per minute at a pressure of anywhere betweenabout 50 and 150 psig.

After the carbon dioxide has been injected into the carrier water C, thecarbon dioxide laden carrier water is subjected to mixing operations toachieve a better uniformity of the carbon dioxide in solution in thecarrier water C. The carbon dioxide laden carrier water first flowsthrough a static mixer 32 for initial mixing of the carrier water-carbondioxide solution. The static mixer 32 typically is isolated from theflow line by ball valves 31. In the preferred embodiment shown in FIGS.1 and 2, parallel static mixers 32 are used, either of which can be usedseparately or in combination with each other. The pressure of thecarrier water-carbon dioxide water solution is measured at variouspoints along the flow line by pressure gauges 30 separated from the flowline by gauge isolation valves 29. After leaving the static mixer 32,the carrier water-carbon dioxide solution flows along a serpentine pipesystem 34 to allow additional mixing and retention time.

An isometric detail view of a typical control panel 50 is shown in FIG.2. These components can be configured as shown in FIG. 2 so as to resultin a stand alone control panel 50 ready for use in a turn-key operation.

The carrier water-carbon dioxide solution exits the control panel 50 andis supplied to the diffusion means 70 through piping 35. Diffusion means70 is inserted into pipe 36 which carries the water W to be treated. Asdiscussed in more detail below, the water W to be treated travelsthrough pipe 36 and past the diffusion means 70, which allows thecarrier water-carbon dioxide solution to diffuse into the water W to betreated.

Referring now to FIGS. 3 and 4, the diffusion means 70 is shown in moredetail. The diffusion means 70 comprises diffuser 71, inlet piping 72,flange 73, and connector pipe 74. Connector pipe 74 attaches to thepiping 35 and allows the carrier water-carbon dioxide solution to enterthe diffusion means 70. Flange 73 allows the diffusion means 70 to besecured, as necessary, to support means (not shown). Inlet piping 72provides access to the carrier water-carbon dioxide solution to thediffuser 71.

Diffuser 71 typically is a triangular prismatic structure which isinserted into pipe 36 such that the prism axis, which is roughlyparallel to the inlet pipe 72 axis, is normal to the pipe 36 axis, andnormal to the direction of flow of the water W to be treated. Thecarrier water-carbon dioxide solution is injected into the center orinterior 76 of diffuser 71. The carrier water-carbon dioxide solution isunder higher pressure than the water W to be treated, such that when thecarrier water-carbon dioxide solution is injected into the interior 76of the diffusers 71, the higher pressure of the carrier water-carbondioxide is maintained within the diffuser. The diffuser is designed tomaintain system pressure until the solution passes through a pluralityof small holes on two rectangular sides, 83, 84. The pressure dropcaused by the carrier water-carbon dioxide solution being forced throughthe plurality of small holes forces excess CO₂ gas from the carrierwater-carbon dioxide solution. This excess CO₂ gas bursts forth as aneffervescence mixing with the water to be treated, thus reducing the pH.The velocity of the saturated solution water passing through smalldiffuser holes, along with the release of excess carbon dioxide gas atthe same time, causes tremendous mixing and immediate chemical reactionwith the main water stream.

The preferred solution injector is a triangular prismatic diffuser 71which is inserted normal to the direction of flow of the water stream W.One triangular end 81 of the diffuser connects to an inlet feed line 72for the solution, while the second triangular end 82 is solid. Two ofthe three rectangular sides 83, 84 of the diffuser 71 have a pluralityof small holes 75 therethrough allowing communication between theinterior 76 of the diffuser 71 and the water stream W. The vertex of twosides 83, 84 faces upstream and the third side 85 faces downstreamrelative to the direction of flow of the water stream W.

The solution, at elevated pressure, is fed to the diffuser 71 through afeed line 35. The pressurized solution, upon encountering the lowerpressure water stream W, equilibrates. Carbon dioxide in the mixturethus expands and comes out of the solution as a gas. As the vertex oftwo sides 83, 84 of the diffuser 71 faces upstream, two sides 83, 84 ofthe diffuser 71 effectively are in the flow path of the water stream W,allowing greater contact between the carbon dioxide gas and the waterstream W. The positioning of the third side 85 of the diffuser 71,facing downstream, creates a vortex in the water stream W flow, thusallowing additional mixing.

The system of the present invention takes carbon dioxide gas at anelevated pressure and injects this gas into a carrier water C, also atan elevated pressure. The amount of carbon dioxide which can be mixedwith water at various temperatures and pressures is known. For example,the volume of carbon dioxide which can dissolve in one volume of wateris shown in Table I.

                  TABLE I    ______________________________________    VOLUMES OF CARBON DIOXIDE DISSOLVED    IN ONE VOLUME OF WATER    Temperature             Pressure, psig (kPa)    °F./°C.             0(0)   20(138) 40(276)                                  60(414)                                        90(621)                                              100(689)    ______________________________________    32/0     1.71   4.0     6.3   8.6   10.9  13.4    40/4.4   1.45   3.4     5.3   7.3   9.2   11.3    60/15.6  1.00   2.3     3.7   5.0   6.3   7.8    80/26.7  0.73   1.7     2.7   3.6   4.6   5.7    100/37.8 0.56   1.3     2.0   2.8   3.5   4.3    ______________________________________

Although any ratio of carbon dioxide to carrier water C allowable underthe laws of nature is appropriate, it has been found that by usingapproximately 60 gallons of carrier water C per pound of carbon dioxidegas, a carrier water having a pH of about 5 which contains excess carbondioxide gas under pressure is created. When this preferred solution isinjected into the water W to be treated through the diffuser 71, theexcess carbon dioxide gas immediately comes out of solution in the formof minute bubbles. These bubbles are released into the main stream ofwater W to be treated, and mixes along with the low pH carrier water Cwith the water to be treated, thus reducing the pH of the water W to betreated.

The solution feed system of the present invention allows accuratecontrol of the pH of water to be treated at a desired level through aprocess in which the water W to be treated also is stabilized at thedesired pH in a very short period of time. Typically, conventional priorart and accepted practice allows for a 20 to 30 minute retention timeafter adding the carbon dioxide in which the water to be treatedstabilizes at the desired pH. In the present system, approximately 95%of the chemical reaction between the water to be treated and the carbondioxide gas is immediate. Thus, very short retention times on the orderof less than 7 minutes, and typically between about 20 seconds and about30 seconds, are required to adjust the pH and stabilize the water W tobe treated using the present system.

In operation, carrier water C at the rate of approximately 60 gallonsper minute minimum for every pound of carbon dioxide gas to be used issupplied to the control panel 50. The carrier water C may be clarifierwater, raw water, finished water or any reasonably clean water supplyavailable. The carrier water C is pumped up to a minimum of 50 psig. Asthe high pressure carrier water C is introduced to the control panels50, carbon dioxide gas is injected into the carrier water C through afine bubble diffuser 80. The carrier water-carbon dioxide mixture thenpasses through in-line static mixers 32 for further mixing. After thestatic mixers 32, the carrier water-carbon dioxide solution passesaround a serpentine pipe system 34 which provides additional contacttime. The carrier water-carbon dioxide solution then travels throughpiping 35 for distribution to the diffusion means 70.

The diffuser 71 has its triangular prismatic shape to allow theinjection of the carrier water-carbon dioxide solution into the water Wto be treated against the flow of the main stream, and to create avortex around and behind the diffuser 71, that is downstream of thewater W to be treated, which helps the carrier water-carbon dioxidesolution mix into the main stream of the water W to be treated. Theinjection of the carrier water-carbon dioxide solution typically occursanywhere from 3 to 7 minutes before the final filter or effluent of thewater W to be treated.

The following Examples illustrate the efficacy of the present system:

EXAMPLE 1

The present system was used to treat a clarifier effluent. The incomingpH of the clarifier effluent was 10.3. The carrier water used wasclarifier water, into which carbon dioxide was fed at the rate of 4.5standard cubic feet per minute per 95 gallons per minute of carrierwater, or approximately one-half pound of carbon dioxide per 95 gallonsof carrier water. The carbon dioxide-carrier water solution was added at50 psig to the open pipeline at the clarifier effluent. The depth of theeffluent trough was about 5 feet. There was about 4 minutes detentiontime in the open pipeline before the treated water arrived at thefilters. 1.2 millions gallons of water were treated. The pH of theclarifier effluent treated with the carbon dioxide-carrier watersolution averaged 8.4. The theoretical carbon dioxide requirement forthis amount of water was 304 pounds per million gallons using an 85%efficiency rate. Only 275 total pounds of carbon dioxide were usedduring this test, resulting in a carbon dioxide requirement of about 230pounds per million gallons. The stability of the treated water was verygood.

EXAMPLE 2

The present system was used to treat a stream of waste water. The wastewater flow rate was between 200 to 500 gallons per minute. The incomingpH of the waste water was 10.5. 1 pound of carbon dioxide per 95 gallonsof carrier water was needed to maintain a final pH of 8.8 in the treatedwater.

EXAMPLE 3

The present system was used to treat a combination effluent. The majorcomponent of the effluent was a mill effluent of 16 million gallons perday having a pH of 10.8. A bleach plant effluent of 8.5 million gallonsper day was added to the mill effluent in a mixing chamber which, attimes, brings the pH of the effluent mixture down to about 9.5. Theeffluent temperature was 115° F. in the summer and 105° F. in thewinter. 5.0 standard cubic feet (about 0.55 pounds) of carbon dioxide in90 gallons of carrier water was able to maintain the pH of the treatedeffluent stream. Retention time was approximately 3 minutes.

EXAMPLE 4

The present system was used to treat the influent to a plant. It wasdesired to reduce the pH of the influent water from 7.3 to a pH of 5.9to 6.0. The influent flow rate was approximately 3.9 million gallons perday. Theoretical calculations indicated that 650 pounds of carbondioxide per million gallons of influent were needed to accomplish thispH. A carbon dioxide-carrier water solution containing 1.5 pounds ofcarbon dioxide per 95 gallons of water was supplied to the influent at60 psig, and was able to maintain the desired pH. The retention time ofthe pipe after the injection of the carbon dioxide-carrier watersolution was approximately 10 seconds.

The above detailed description of a preferred embodiment and examplesare for illustrative purposes only and are not intended to limit thescope and spirit of the invention or its equivalents as defined in thefollowing claims.

What is claimed:
 1. An apparatus for introducing a gas comprising carbondioxide into a liquid stream flowing through a pipe to reduce the pH ofsaid liquid stream, comprising:a. means for providing said gas at afirst flow rate and a first pressure between about 30 and 300 psig; b.means for providing a carrier liquid comprising water at a second flowrate and a second pressure which is a minimum of 50 pisg; c. means formixing said gas and said liquid at an elevated pressure greater than thepressure of said liquid stream to form a supersaturated carbondioxide-water solution; d. means for maintaining said solution at saidelevated pressure until introduced into said liquid stream; and e.diffusion means inserted into said pipe for introducing said solutioncontinuously into said liquid stream, releasing excess carbon dioxidefrom said solution into said liquid stream, wherein said diffusion meanscomprises a solution inlet means and a diffuser means, said diffusermeans comprising a generally hollow interior and generally solid walls,said walls comprising a plurality of holes therethrough allowingcommunication between said interior and the exterior.
 2. The apparatusas claimed in claim 1, wherein said means for providing said gas furthercomprises a means for regulating the flow rate of said gas.
 3. Theapparatus as claimed in claim 2, wherein said means for mixing comprisesa static mixer.
 4. The apparatus as claimed in claim 3, wherein saidmeans for mixing further comprises a contact area.
 5. An apparatus forreducing the pH of a water stream flowing through a pipe, comprising;a.means for providing a continuous flow of a gas comprising carbon dioxideat a first flow rate and a first pressure between about 30 and 300 psig;b. means for adjusting said first flow rate and means for adjusting saidfirst pressure; c. means for providing a liquid comprising water at asecond flow rate and a second pressure which is a minimum of 50 psig; d.means for adjusting said second flow rare and means for adjusting saidsecond pressure; e. means for mixing said gas and liquid to form asupersaturated carbon dioxide-water solution at a third pressure andhaving a first pH; f. means for providing said water stream at apressure less than said first and third pressures and having a second pHgreater than said first pH; g. means for maintaining said solution atsaid third pressure until introduced into said water stream; and h.diffusion means inserted into said pipe for introducing said solutioncontinuously into said water stream, releasing excess carbon dioxidefrom said solution into said water stream to reduce the pH of said waterstream, wherein said diffusion means comprises a solution inlet meansand a diffuser means, said diffuser means comprising a generally hollowinterior and generally solid walls, said walls comprising a plurality ofholes therethrough allowing communication between said interior and theexterior.
 6. The apparatus as claimed in claim 5, further comprising ameans for injecting said gas into said liquid.
 7. The apparatus asclaimed in claim 6, wherein said diffuser means has a generallytriangular prismatic structure, said diffuser means being inserted intosaid liquid stream with one of said walls facing downstream relative tothe direction of flow of said liquid stream.
 8. A system for reducingthe pH of a water stream flowing through a pipe, comprising:a. means forstoring a gas comprising carbon dioxide at a selected temperature andpressure between about 30 and 300 psig; b. means for continuouslysupplying said gas at a selected flow rate and pressure; c. means forsupplying a liquid comprising water at a selected flow rate and pressurewhich is a minimum of 50 psig; d. means for introducing said gas intosaid liquid; e. means for mixing said gas with said liquid to form asupersaturated carbon dioxide-water solution; f. means for maintainingsaid solution at a pressure greater than that of said water stream untilintroduced into said water stream; and g. diffusion means inserted intosaid pipe for continuously introducing said solution into a watersystem, thereby releasing excess carbon dioxide from said solution intosaid water stream to reduce the pH of said water stream, wherein saiddiffusion means comprises a solution inlet means and a diffuser means,said diffuser means comprising a generally hollow interior and generallysolid walls, said walls comprising a plurality of holes therethroughallowing communicating between said interior and the exterior.
 9. Thesystem as claimed in claim 8, further comprising:a. means for measuringthe pH of said water stream subsequent to the introduction of saidsolution; b. means for comparing said pH measurement to a desired pHlevel; and c. means for adjusting said flow rate of said gas wherebysaid flow rate of said gas is continually adjusted until said pHmeasurement is substantially equal to said desired pH level.